This application is based on, claims the benefit of priority of, and incorporates by reference the contents of prior Japanese Patent Application No. 2001-340629, filed on Nov. 6, 2001, and No. 2002-238133, filed on Aug. 19, 2002.
1. Field of the Invention
The present invention relates to a structure for a spraying tip or end of a fuel injection valve that is applicable to a fuel injection valve that supplies fuel to an intake pipe of, for example, an internal combustion engine.
2. Description of the Related Art
Generally, fuel injection valves are known which, for example, are provided at the intake pipe of an internal combustion engine to supply fuel to the engine. Japanese Patent Laid-Open Publication Nos. Hei. 8-277763 and 9-310651 are examples of such a technology.
With improvements in the performance of internal combustion engines, there is a demand for cleaner exhaust emissions in connection with the fuel injection valves of this kind. In particular, improved valves are needed to further vaporize fuel so that the injected fuel spray is comprised of finer particles.
Japanese Patent Laid-Open Publication No. Hei. 8-277763 discloses means for achieving the above purpose. According to the disclosure of the document, a nozzle needle as a valve member forms a flow path that directs fuel toward an injection hole plate in cooperation with the internal circumferential wall of a nozzle body as a valve body. An extension of the tip of the nozzle needle at the outer circumference is positioned outside the circular shape of a plurality of injection holes provided at the tip of the nozzle body at the opening on the inlet side. After fuel strikes the tip of the nozzle body, in other words, the injection hole plate, the fuel forms streams toward the center along the upper surface of the injection hole plate, and the fuel is ejected from the injection holes provided on the way to the center.
According to Japanese Patent Laid-Open Publication No. Hei. 9-310651, while the streams toward the center are formed, the injection holes are provided in slanted directions so that the streams formed toward the injection holes do not interfere with each other around the center of the injection hole plate and do not impede the flow of injection.
In conventional arrangements, the fuel passes at an increased speed into the injection hole inlets positioned on the upper surface of the injection hole plate at the tip of the fuel injection valve. Therefore, the kinetic energy of the injected fuel can be increased and the fuel spray will be fine particles. However, the vacuum air stream in the intake pipe is mixed with the fuel spray injected from the injection holes and forms an air-fuel mixture. The conventional arrangements do not fully take into account the effect of this air stream upon fuel spraying.
Meanwhile, there is a known valve that includes a sleeve provided at the lower surface of the injection hole plate having openings concentric to the group of injection holes at the injection hole plate and having an enlarged diameter (see Japanese Patent Laid-Open Publication No. 2000-145589). According to Japanese Patent Laid-Open Publication No. 2000-145589, the sleeve is made of a resin material and press-fitted onto the outer periphery of the tip end of the fuel injection valve to make it secure.
However, the holding strength to fix the sleeve could be lowered by high temperature creep, etc., and its engagement to the outer periphery of the end of the injection valve could become loose or undone, permitting the sleeve to rotate. Meanwhile, in order to provide the holding strength by press-fitting, excessive compressive stress could be provided to the valve body that forms the end, so that the valve can not be closed as tightly as required when in a fully closed state.
When the holding strength by press fitting is low, the operator might inadvertently rotate the sleeve from a desired position when the injection fuel valve is attached.
In view of the foregoing disadvantages, it is an object of an embodiment of the present invention to provide a fuel injection valve that generates smaller fuel spray particles and permits the valve to be tightly closed and readily assembled by press-fitting. Another object of an embodiment of the present invention is to prevent excessive stresses from being subjected to the valve portion to prevent the sleeve from rotating.
According to a first aspect of the invention, a fluid injection valve includes an injection hole plate provided at a fluid path outlet formed at a tip portion of an end of a valve body, the plate having a plurality of injection holes. Furthermore, a sleeve is fixed to the valve body provided with the injection hole plate. The fluid injection valve injects fluid from the injection holes to control the amount of the fluid and determine the injection direction. The valve body has a bottom wall portion with a valve seat against/from which a valve member abuts/moves away, and a side wall portion provided upright from a peripheral edge of the bottom wall portion that supports the valve member in a reciprocating manner.
The injection hole plate is formed as a cup shape, has its entire circumference joined to the valve body to cover the fuel path, and has a bottom portion with the injection holes to allow the fuel path to communicate with an area outside of the valve structure. There is also a cylindrical portion provided upright from a peripheral edge of the bottom portion and press-fitted onto the side wall portion. The sleeve is a resin sleeve having a resin annular portion with an opening opened toward the downstream side of the fuel injected from the injection hole plate, and a resin cylindrical portion provided upright from a peripheral edge of the resin annular portion and press-fitted onto the side wall portion. One of the sleeve and the injection hole plate has a projection and the other has a cutout groove corresponding to the projection so that the sleeve and the injection hole plate may engage each other.
In general, in a resin sleeve having an opening opened toward the downstream side of fuel injected from the injection hole plate, its holding strength, kept fittingly fixed to the valve body, may be lessened depending upon the state of any high temperature creep as it is press-fitted onto the side wall of the valve body. This could cause the engagement of the sleeve to the outer periphery of the valve body to become undone. Additionally, in order to provide holding strength by press-fitting, excessive compressive stress could be induced into the valve body. Then, the valve may not be able to close as tightly as required in a fully closed state depending upon how much additional pressing force is provided to the sleeve to compensate for the decrease in the holding strength caused by the high temperature creep.
In contrast, in the fuel injection valve according to the invention, one of the sleeve and the injection hole plate has a projection and the other has a cutout groove corresponding to the projection so that the sleeve and the injection hole plate may engage each other. Therefore, without increasing the force of press-fitting the sleeve to compensate for the decrease in the holding strength due to any high temperature creep as in the conventional manner, the outer circumference of the valve body and the sleeve can securely be engaged with each other and the sleeve can be prevented from rotating.
Therefore, the valve tightness in a fully closed state can be secured, while the valve body and the sleeve can be engaged without increasing the force of press-fitting the sleeve. The valve body and the sleeve can more readily be assembled by press-fitting.
According to a second aspect of the invention, in providing the projection to the injection hole plate and the cutout groove corresponding to the projection, to the sleeve, the resin cylindrical portion, press-fitted onto the side wall portion, includes a press-fitting portion that can be press-fitted onto the side wall portion at an axial end. The cutout groove having a shape that engages with the projection is provided at the inner circumference between the press-fitting portion and the annular resin portion. The cylindrical portion press-fitted onto the side wall portion is provided with the projection, corresponding to the cutout groove, at the outer circumference of the cylindrical portion.
More specifically, a press-fitting portion that can be press-fit onto the side wall portion is provided at an axial end of the resin cylindrical portion of the sleeve. The cutout groove having a shape that engages with the projection is provided at the inner circumference of the sleeve between the press-fitting portion and the resin annular portion. The inner circumference of the cylindrical portion of the injection hole plate is press-fit onto the side wall portion and the projection corresponding to the cutout groove is provided at the outer circumference of the cylindrical portion. In this way, without increasing the force of press-fitting the sleeve, the valve body and the sleeve can more easily engage each other.
According to a third aspect of the invention, in addition to providing the projection of the cylindrical portion of the injection hole plate which corresponds to the cutout groove of the sleeve, a press-fitting portion that can be press-fitted onto the side wall portion at an axial end of the sleeve and the valve body is provided. The projection is provided at the inner circumference of the sleeve between the press-fitting portion and the resin annular portion. The cylindrical portion press-fitted onto the side wall portion is provided with the cutout groove having a shape that engages the projection at the outer circumference of the cylindrical portion.
More specifically, in addition to a cutout groove corresponding to a projection provided, a press-fitting portion that can be press-fitted onto the side wall portion is provided at an axial end of the resin cylindrical portion of the sleeve. The projection is provided at the inner circumference between the press-fitting portion and the resin annular portion. The inner circumference of the cylindrical portion of the injection hole plate is press-fitted onto the side wall portion and the cutout groove corresponding to the projection is provided at the outer circumference of the cylindrical portion of the injection hole plate. In this way, without increasing the force of press-fitting the sleeve, the outer periphery of the valve body and the sleeve can more securely engage each other.
Note that the cutout groove is provided adjacent to the cylindrical portion and press-fit onto the side wall portion. Therefore the rigidity of the cylindrical portion can be reduced because of the cutout groove. Therefore, the strength for holding the injection hole plate press-fitted onto the side wall portion of the valve body may be reduced. In this way, the inner circumference of the valve body is deformed less by the press fitting that affects the valve tightness in a fully closed state. Therefore, the valve tightness in a fully closed state can be improved.
According to a fourth aspect of the invention, the press-fitting portion is provided at approximately an equal pitch at the inner circumference of the resin cylindrical portion, and the projection and the press-fitting portion are arranged so that their circumferential positions do not overlap. More specifically, in the resin sleeve, the press-fitting portion press-fitted to the valve body, is provided at about an equal pitch at the inner circumference of the resin cylindrical portion. Additionally, the projection and the press-fitting portion are arranged so that their circumferential positions do not overlap. In this way, the projection formed at the inner circumference of the sleeve and the press-fitting portion are arranged so that their circumferential positions do not overlap or coincide. Therefore, the sleeve can more readily be resin-molded.
According to a fifth aspect of the invention, an annular rib is formed at the axial end of the cylindrical portion, and the cutout groove provided adjacent to the cylindrical portion is provided at the rib. More specifically, the annular rib is formed at the axial end of the cylindrical portion of the injection hole plate that is formed into a cup shape. The cutout groove is provided at the rib, and therefore such a cutout does not have to be provided during press-working of the cup-shaped injection hole plate into the developed form. The injection hole plate in the developed form is subjected to deep-drawing and formed into a cup shape followed by press punching to the thin plate member. At that time, the cutout groove can be formed at the annular rib. Therefore, when the injection hole plate is subjected to deep drawing, the injection hole plate does not have a cutout groove that might lower the rigidity of the injection hole plate in the developed form, and the injection hole plate can readily be produced.
According to a sixth aspect of the invention, the projection provided at the cylindrical portion is made of a rib extending in the radial direction from the axial end of the cylindrical portion of the injection hole plate. In this way, similarly to the fifth aspect, the injection hole plate can more readily be provided with the projection.
According to a seventh aspect of the invention, the opening has an approximately elliptical shape. Generally, when the opening of the sleeve opened to the downstream side of the fuel injected from the injection hole plate has approximately an elliptical shape, the distance from the outlets of the injection holes formed at the lower surface of the injection hole plate to the inner circumference of the opening portion may vary depending upon the circumferential positions where the sleeve is engaged with the valve body or the injection hole plate. Therefore, when the fuel injection valve has an opening of this kind, fuel injected from injection holes could interfere with the inner circumference of the opening depending upon the circumferential position where the sleeve is engaged with the injection hole plate.
In contrast, in the fuel injection valve according to the present invention, when the sleeve and injection hole plate are press-fitted onto the valve body for assembly, either the sleeve or the injection hole plate is provided with projections, and the other is provided with the cutout grooves corresponding to the projections, so that they may engaged each other. Therefore, the engagement between the injection hole plate and the sleeve around their circumferential interface is not undone. Therefore, injected fuel does not interfere with the inner circumference of the opening by shifts caused in the assembled state between the injection hole plate and the sleeve.
According to an eighth aspect of the invention, the injection holes are preferably arranged annularly and are not symmetrical with respect to the fuel injection valve axis, but line-symmetrical on the injection hole plate, such that axial lines of the injection holes radially extend toward the downstream side with respect to the axial direction of the fuel injection valve.
According to a ninth aspect of the invention, a fuel injection valve includes a valve body provided with a valve seat at an inner wall surface of the valve body. A fluid path is formed and a valve member seating at the valve seat opens and closes the fluid path adjacent an injection hole plate attached to the valve body on the fluid downstream side of the valve member. The injection hole plate has a plurality of injection holes and a cup-shaped sleeve is attached to the valve body to cover the outer circumference of the injection hole plate.
The fuel injection valve injects fuel from the injection holes. The sleeve has an opening from which fuel injected from the injection holes is discharged. One of the sleeve and the injection hole plate is provided with a projection, while the other is provided with a cutout groove corresponding to the projection, so that the sleeve and the injection hole plate may engage with each other. In this way, if the sleeve is allowed to rotate, the inner circumferential surface of the cutout groove abuts against the outer circumferential surface of the projection, and therefore excessive stress upon the valve portion can be prevented as much as possible while the sleeve can be prevented from rotating.
According to a tenth aspect of the invention, a plurality of the projections and the cutout grooves are provided around the outer circumference of the cylindrical portion of the injection hole plate and the inner circumference of the sleeve. Therefore, a plurality of fitting portions are provided, and the sleeve can be prevented from rotating.
According to an eleventh aspect of the invention, the sleeve is provided with a projection projecting radially inward at the inner circumferential surface of the sleeve, and the injection hole plate is provided with a cutout groove engaged with the projection at the outer circumferential surface of the injection hole plate.
According to a twelfth aspect of the invention, the present invention may preferably be applied to the fuel injection valve with an opening formed into an approximately elliptical shape. Alternatively, according to a thirteenth and fourteenth aspect of the invention, there may be a negative pressure generating portion for generating negative pressure by flowing fuel from the opening to draw fuel adhering to the sleeve outer circumferential surface.
The injection valve spray characteristics can be degraded if the sleeve rotates. Meanwhile, in the fuel injection valve according to twelfth to fourteenth aspects of the invention, the sleeve can be prevented from rotating and therefore the advantages are significant.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.